Driving circuit and voltage modulation method

ABSTRACT

The present disclosure provides a driving circuit, configured to couple to a light emitting diode (LED) and a power supply circuit. The driving circuit includes a comparator, a serial input interface, and an integrating unit. The comparator is configured to couple to the LED and determine whether a cathode voltage of the LED is lower than a threshold value and generate a monitoring data. The serial input interface is configured to receive a serial input data from a previous driving circuit. The integrating unit is coupled to the comparator and the serial input interface and configured to integrate the monitoring data and the serial input data to generate an output data. The output data is transmitted to a following driving circuit or feedbacked to the power supply circuit in order to modulate a power voltage that the power circuit provides to the LED.

CROSS - REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application SerialNo. 63/264,046, filed Nov. 15, 2021, which is herein incorporated byreference in its entirety.

BACKGROUND Field of Invention

The present invention relates to a driving circuit and a voltagemodulation method. More particularly, the present invention relates to adriving circuit and a voltage modulation method both able to modulate apower voltage.

Description of Related Art

For most display devices on the market, the driver integrated circuits(IC) that control the currents passing through the light emitting diodes(LEDs) in the display device need a common bus system in order tocommunicate information about whether the driving voltage is largeenough to drive the LEDs. In this approach, extra pins are required forall driver ICs in order to communicate through the common bus system,and thus the cost and complexity to manufacture the driver ICs increase.

SUMMARY

The present disclosure provides a driving circuit, coupled to a lightemitting diode and a power supply circuit and configured to control thepower supply circuit to provide power to the light emitting diode. Thedriving circuit includes a comparator, a serial input interface, and anintegrating unit. The comparator is coupled to the light emitting diodeand configured to determine whether a voltage at the light emittingdiode’s cathode is lower than a threshold value and to generate amonitoring data. The serial input interface is configured to receive aserial input data from a previous driving circuit. The integrating unitis coupled to the comparator and the serial input interface andconfigured to integrate the monitoring data and the serial input data togenerate an output data. The output data is transmitted to a followingdriving circuit or feedbacked to the power supply circuit in order tomodulate a power voltage provided by the power circuit provides to thelight emitting diode.

The present disclosure also provides a voltage modulation method,including determining whether a cathode voltage of a light emittingdiode is lower than a threshold value and generating a monitoring data;receiving a serial input data from a previous driving circuit;integrating the monitoring data and the serial input data to generate anoutput data; and transmitting the output data to a following drivingcircuit or feeding back the output data to a power supply circuit inorder to modulate a power voltage that the power circuit provides to thelight emitting diode.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 is a circuit diagram of a display device in accordance with someembodiments of the present disclosure.

FIG. 2 is a circuit diagram of a driving circuit in accordance with someembodiments of the present disclosure.

FIG. 3A is a time sequence diagram of signals that a driving circuittransmits and receives in accordance with some embodiments of thepresent disclosure.

FIG. 3B is a time sequence diagram of signals that a driving circuittransmits and receives in accordance with some embodiments of thepresent disclosure.

FIG. 3C is a time sequence diagram of signals that a driving circuittransmits and receives in accordance with some embodiments of thepresent disclosure.

FIG. 3D is a time sequence diagram of signals that a driving circuittransmits and receives in accordance with some embodiments of thepresent disclosure.

FIG. 3E is a time sequence diagram of signals that a driving circuittransmits and receives in accordance with some embodiments of thepresent disclosure.

FIG. 4 is a circuit diagram of a driving circuit in accordance with someembodiments of the present disclosure.

FIG. 5 is a circuit diagram of a driving circuit in accordance with someembodiments of the present disclosure.

FIG. 6 is a flowchart of a voltage modulation method in accordance withsome embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are described herein and illustrated inthe accompanying drawings. While the disclosure will be described inconjunction with embodiments, it will be understood that they are notintended to limit the disclosure to these embodiments. On the contrary,the disclosure is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of thedisclosure as defined by the appended claims. It is noted that, inaccordance with the standard practice in the industry, the drawings areonly used for understanding and are not drawn to scale. Hence, thedrawings are not meant to limit the actual embodiments of the presentdisclosure. In fact, the dimensions of the various features may bearbitrarily increased or reduced for clarity of discussion. Whereverpossible, the same reference numbers are used in the drawings and thedescription to refer to the same or like parts for better understanding.

Please refer to FIG. 1 . FIG. 1 is a circuit diagram of a display device100 in accordance with some embodiments of the present disclosure. Thedisplay device 100 includes multiple driving circuits 110, a powersupply circuit 120, a control unit 130, and multiple light emittingdiodes (LEDs) 140 coupled between the power supply circuit 120 and thecorresponding driving circuits 110. In one embodiment, the displaydevice 100 is a display panel, a touch panel, a television or a smarttelevision including a LED backlight module or a colored LED panel.

In some embodiments, the power supply circuit 120 is configured toprovide a power voltage VLED to anodes of the light emitting diodes 140.In one embodiment, the power supply circuit 120 is a DC-to-DC converteror a low-dropout (LDO) regulator.

In some embodiments, one of the driving circuits 110 (e.g., the latestdriving circuits 110 c in the embodiment shown in FIG. 1 ) is coupledwith the power supply circuit 120 and the driving circuit 110 c isconfigured to generate a feedback control signal SFB to the power supplycircuit 120 for modulating the power voltage VLED provided by the powersupply circuit 120.

Each driving circuit 110 electrically connects to a plurality of LEDs140. In the embodiment shown in FIG. 1 , each driving circuit 110connects to two columns of LEDs 140. As shown in FIG. 1 , the drivingcircuit 110 a connects to the LED columns A and B, the driving circuit110 b connects to the LED columns C and D, and the driving circuit 110 cconnects to the LED columns E and F. It should be noted that the numberof the LED columns is merely exemplary. In some embodiments, the drivingcircuits 110 electrically connect to an array of LEDs 140 that consistsof more than six columns of LEDs 140.

In one embodiment, the control unit 130 includes a data driver forproviding display data DD to be displayed on the array of LEDs 140 inthe display device 100 and also a time controller (TCON) configured totransmit clock signals to the driving circuits 110.

In some embodiments, the driving circuits 110 are configured to controldriving currents passing through the LEDs 140 according to the displaydata DD. Specifically, the control unit 130 generates the display dataDD and passes it to the driving circuits 110 a, 110 b, and 110 c througha serial transmission. According to such display data DD, the drivingcircuit 110 a controls the currents of the LEDs 140 in the LED columns Aand B, the driving circuit 110 b controls the currents of the LEDs 140in the LED columns C and D, and the driving circuit 110c controls thecurrents in the LEDs 140 of the LED columns E and F.

In the embodiment shown in FIG. 1 , there are only three drivingcircuits 110, i.e., the driving circuits 110 a, 110 b, 110 c. It shouldbe noted that the number of the driving circuits 110 in the displaydevice 100 is merely exemplary, and person having ordinary skills in theart can modify such number according to actual needs or design.

In some embodiments, the display data DD generated by the control unit130 contain data about the images that will be displayed through theLEDs 140. For example, the display data DD transmitted to the drivingcircuit 110 a can define the brightness of the LEDs 140 in the LEDcolumns A and B. In some embodiments, the display data DD carry a seriesof brightness codes, e.g., [0, 155, 30, 34, 50, 70], and the codescorrespond to the LED columns A, B, C, D, E, and F. Specifically, thedriving circuit 110 a will receive the codes [0, 155] and control thebrightness of the LED columns A and B correspondingly, the drivingcircuit 110 b will receive the codes [30, 34] and control the brightnessof the LED columns C and D correspondingly, and the driving circuit 110c will receive the codes [50, 70] and control the brightness of the LEDcolumns E and F correspondingly. In other words, the display data DDrepresent the brightness of the LEDs 140. In some embodiments, thedisplay data DD are about the image frame to be displayed through theLED array.

The power supply circuit 120 is configured to drive the LEDs 140 in thedisplay device 100. Specifically, the power supply circuit 120 generatesthe power voltage VLED and provides it to the anode of the topmost LED140 in each LED column, such as the LED 140 b 1 in the LED column C.When the power voltage VLED is large enough to create sufficient voltagedifference between the two ends of each LED columns A, B, C, D, E, andF, all LEDs 140 in the display device 100 can operate properly.Specifically, one LED 140 is able to operate in light-emitting when thevoltage difference between its anode and cathode is greater than orequal to the forward voltage (Vf) of that LED 140, so in order to drivemultiple LEDs 140 coupled in series in one LED column, e.g., the LEDs140 b 1~140 bn in the LED column C, the power voltage VLED has to beequal to or greater than n*Vf.

Because the forward voltages (Vf) for each of the LEDs 140 can beslightly different due to a manufacturing bias or a temperatureconduction, if the power voltage VLED provided by the power supplycircuit 120 is fixed, the fixed power voltage VLED may not be highenough to light up all LEDs 140 in every LED column. However, if thepower supply circuit 120 provides the power voltage VLED with arelatively higher level that is way over a required level needed by theLED array, it will cost extra power consumption and be not powerefficient. In some embodiments, the driving circuits 110 are able todetect cathode voltages on these LED columns and generate the feedbackcontrol signal SFB to the power supply circuit 120 for modulating thepower voltage VLED (e.g., raising a voltage level of the power voltageVLED).

The mechanism for modulating the power voltage VLED is discussed below.Please refer to FIG. 1 and FIG. 2 . FIG. 2 is a circuit diagram of thedriving circuit 110 b in accordance with some embodiments of the presentdisclosure. Here, the driving circuit 110 b shown in FIG. 1 is used asan example for explanatory purpose. The other driving circuit 110, suchas the driving circuit 110 a, can have the same components as thedriving circuit 110 b shown in FIG. 2 .

The driving circuit 110 b includes a comparator 111, a serial inputinterface 112, and an integrating unit 113. As shown in FIG. 1 and FIG.2 , the driving circuit 110 b is coupled to the driving circuit 110 aand the driving circuit 110 c. For the purpose of simplicity, in theembodiment shown in FIG. 2 , only the LED column C couples to thedriving circuit 110 b, and the LED column D shown in FIG. 1 is omittedhere. Thus, in the embodiment shown in FIG. 2 , the driving circuit 110b is coupled to the LED column C (not shown in FIG. 1 ), specifically tothe LED 140bn.

The comparator 111 is coupled to the LED 140 bn and configured todetermine whether the cathode voltage of the LED 140 bn (i.e., thevoltage at the node N) is lower than a threshold value and to generate amonitoring data Dmon. Specifically, the comparator 111 receives thevoltage at the node N and compares it with the predetermined thresholdvalue, in order to determine whether a higher voltage should be providedto the LED 140 bn (i.e., whether the power voltage VLED configured todrive all LEDs 140 in the display device 100 needs to be stepped up). Inone embodiment, the threshold value is predetermined by the designer ormanufacturer of the display device 100.

In one embodiment, when the comparator 111 determines that the voltageat the node N is lower than the threshold value, the monitoring dataDmon has a first level, while when the comparator 111 determines thatthe voltage at the node N is higher than the threshold value, themonitoring data Dmon has a second level. The monitoring data Dmon havingthe first level indicates that the power voltage VLED needs to bestepped up, and the monitoring data Dmon having the second levelindicates that the power voltage VLED is large enough and does not needto be raised. In one embodiment, the monitoring data is a digital data,the first level is high logic level, and the second level is low logiclevel. In one embodiment, the monitoring data is an analog data, thefirst level is a higher voltage level, and the second level is lowervoltage level.

The serial input interface 112 is configured to receive a serial inputdata SDI from a previous driving circuit, i.e., the driving circuit 110a in the embodiment shown in FIG. 2 . The serial input data SDI includeboth the display data DD generated by the control unit 130 as shown inFIG. 1 and the data about the cathode voltages of the LEDs 140 that aremonitored by the driving circuit 110 a. As previously discussed, thedriving circuit 110 a has the same components as the driving circuit 110b and thus the driving circuit 110 a includes the comparator 111configured to monitor cathode voltages of the LEDs 140 coupled to it.How the display data DD and the data about the voltage of the LEDs 140monitored by the driving circuit 110 a are transmitted through theserial input data SDI in different time periods will be discussed inlater paragraphs. Below first discuss how the data about the voltage ofthe LEDs 140 monitored by the driving circuit 110 a and the data aboutthe voltage of the LEDs 140 monitored by the driving circuit 110 b areintegrated.

The integrating unit 113 is coupled to the comparator 111 and the serialinput interface 112 and configured to integrate the monitoring data Dmonand the serial input data SDI to generate an output data SDO. The outputdata SDO is then transmitted to a following driving circuit, which isthe driving circuit 110 c in this embodiment. The monitoring data Dmonindicate that whether the power voltage VLED is sufficiently large todrive the LED column C, and the serial input data SDI indicate thatwhether the power voltage VLED is sufficiently large to drive the LEDs140 coupled to the driving circuit 110 a (e.g., the LEDs 140 of the LEDcolumns A and B in FIG. 1 ). Thus, the integrating unit 113 isconfigured to combine the information about the cathode voltagesmonitored by the driving circuits 110 a and 110 b and pass suchinformation to the driving circuit 110 c.

Specifically, in one embodiment, the integrating unit 113 sets theoutput data SDO as the first level when the monitoring data Dmon has thefirst level or the serial input data SDI has the first level. That is,when either of the monitoring data Dmon and the serial input data SDIhas the first level, the output data SDO generated by the integratingunit 113 has the first level. In other words, when either of the drivingcircuit 110 a and the driving circuit 110 b determines that the powervoltage VLED is not sufficient to drive the LEDs 140 coupled to them andthat the power voltage VLED needs to be stepped up, the output data SDOis set as the first level. The output data SDO generated by theintegrating unit 113 with the first level is configured to trigger thepower supply circuit 120 to raise the power voltage VLED. On the otherhand, in one embodiment, the integrating unit 113 sets the output dataSDO as the second level when both the monitoring data Dmon and theserial input data SDI have the second level. In other words, when bothof the driving circuit 110 a and 110 b determine that the power voltageVLED is sufficient to drive the LEDs 140 coupled to them and that thepower voltage VLED does not need to be stepped up, the output data isset as the second level. The output data SDO generated by theintegrating unit 113 with the second level is configured to trigger thepower supply circuit 120 to maintain the power voltage VLED. These twoembodiments can also be understood through the embodiments in FIGS. 3A,3B, 3C, 3D, and 3E. More details will be discussed in later paragraphs.

In one embodiment, the serial input data SDI and/or the output data SDOis a digital data, the first level is high logic level, and the secondlevel is low logic level. In one embodiment, the serial input data SDIand/or the output data SDO is an analog data, the first level is ahigher voltage level, and the second level is lower voltage level.

In one embodiment, the output data SDO is transmitted to a serial outputinterface 114 as shown in FIG. 2 , and the serial output interface 114transmits the output data SDO to the driving circuit 110 c. Therefore,through the combination and operation of the components of the drivingcircuit 110 b, the information about the voltage of the LEDs 140 coupledto the driving circuit 110 a (which is contained in the serial inputdata SDI) and the information about the voltage of the LEDs 140 coupledto the driving circuit 110 b (which is contained in the monitoring dataDmon) can be integrated together and passed to the driving circuit 110 cin the form of the output data SDO. In some embodiments, the output dataSDO can be referred to as a multi-chip communication signal, whichcontains the information collected by more than one chip (i.e., thedriving circuit 110 in the present disclosure).

Please refer to FIG. 2 and FIG. 3A. FIG. 3A is a time sequence diagramof the signals that the driving circuit 110 b transmits and receives inaccordance with some embodiments of the present disclosure. As pointedout in the paragraphs above, the display data DD is also contained inthe serial input data SDI. To be more specific, in one embodiment, theintegrating unit 130 integrates the monitoring data Dmon and the serialinput data SDI in a time-dividing manner, in which the integrating unit130 bypasses the display data DD carried in the serial input data SDI asthe output data SDO during a first period P1 and combines the monitoringdata Dmon with the serial input data SDI as the output data SDO during asecond period P2. The first period P1 and the second period P2 do notoverlap.

The serial input data SDI in FIG. 3A are the data received by the serialinput interface 112 of the driving circuit 110 b as shown in FIG. 2 ,the monitoring data Dmon in FIG. 3A are the data monitored by thecomparator 111 and transmitted to the integrating unit 113 as shown inFIG. 2 , and the output data SDO in FIG. 3A are the data generated bythe integrating unit 113 as shown in FIG. 2 . The control signal Scon inFIG. 3A is configured to control the driving circuit 110 b to operate inthe first period P1 or the second period P2. In one embodiment, thecontrol signal Scon is provided by the control unit 130 as shown in FIG.1 . In the embodiment shown in FIG. 3A, the display data DD is a squarewave during the first period P1. It is worth noted that the square waveof the display data DD shown in FIG. 3A is merely exemplary, and thatthe display data DD can have a waveform other than the square wave.During the first period P1, the control signal Scon has a low logiclevel and the driving circuit 110 b operates in the first period P1.During the second period P2, the control signal Scon has a high logiclevel and the driving circuit 110 b operates in the second period P2.

As shown in FIG. 3A, the display data DD is transmitted through theserial input data SDI during the first period P1, and the monitoringdata DmonA is transmitted through the serial input data SDI during thesecond period P2. The monitoring data DmonA refer to the monitoring datathat the comparator 111 of the driving circuit 110 a generates accordingto the cathode voltage of the LEDs 140 coupled to the driving circuit110 a, and the monitoring data DmonA is transmitted to the drivingcircuit 110 b from the serial output interface 114 of the drivingcircuit 110 a. The monitoring data DmonB refer to the monitoring datathat the comparator 111 of the driving circuit 110 b generates andtransmits to the integrating unit 113 of the driving circuit 110 b. Theoutput data SDO refer to the data that the integrating unit 113 of thedriving circuit 110 b generates by integrating the monitoring data Dmonand the serial input data SDI in the time-dividing manner mentionedabove.

Specifically, in the embodiment shown in FIG. 3A, during the firstperiod P1, the display data DD is transmitted through the serial inputdata SDI, and, although the integrating unit receives the monitoringdata DmonB, because the integrating unit 113 does not combine themonitoring data Dmon with the serial input data SDI during the firstperiod P1, the integrating unit 113 simply outputs the display data DDas the output data SDO.

During the second period P2, the monitoring data DmonA is transmittedthrough the serial input data SDI, and because the integrating unit 113combines the monitoring data Dmon with the serial input data SDI as theoutput data SDO during the second period P2, the integrating unit 113integrates the monitoring data DmonA and the monitoring data DmonB intothe monitoring data DmonC in the second period P2.

In one embodiment, the serial input interface 112, the integrating unit113, and the serial output interface 114 operate in the second period P2when the control signal Scon has the first level, and the serial inputinterface 112, the integrating unit 113, and the serial output interface114 operate in the first period P1 when the control signal Scon has thesecond level. In one embodiment, the first level is high logic level,and the second level is low logic level.

Please refer to FIG. 3B. FIG. 3B is a time sequence diagram of thesignals that the driving circuit 110 b transmits and receives inaccordance with some embodiments of the present disclosure. In oneembodiment, the serial input data SDI during the second period P2 (i.e.,the monitoring data DmonA in FIG. 3A) has a high voltage level, whichindicates that according to the cathode voltage monitored by thecomparator 111 of the driving circuit 110 a the power voltage VLED needsto be stepped up; the monitoring Dmon has a low voltage level, whichindicates that according to the cathode voltage monitored by thecomparator 111 of the driving circuit 110 b the power voltage VLED doesnot need to be stepped up. Therefore, the output data SDO during thesecond period P2 (i.e., the monitoring data DmonC in FIG. 3A) has a highvoltage level as the output data SDO is generated by combining theserial input data SDI and the monitoring data Dmon during the secondperiod P2.

Please refer to FIG. 3C. FIG. 3C is a time sequence diagram of thesignals that the driving circuit 110 b transmits and receives inaccordance with some embodiments of the present disclosure. In oneembodiment, the serial input data SDI during the second period P2 has alow voltage level, which indicates that according to the cathode voltagemonitored by the comparator 111 of the driving circuit 110 a the powervoltage VLED does not need to be stepped up; the monitoring Dmon has ahigh voltage level, which indicates that according to the cathodevoltage monitored by the comparator 111 of the driving circuit 110 b thepower voltage VLED needs to be stepped up. Therefore, the output dataSDO during the second period P2 has a high voltage level.

Please refer to FIG. 3D. FIG. 3D is a time sequence diagram of thesignals that the driving circuit 110 b transmits and receives inaccordance with some embodiments of the present disclosure. In oneembodiment, both the serial input data SDI and the monitoring Dmonduring the second period P2 have high voltage levels. Therefore, theoutput data SDO during the second period P2 has a high voltage level.

Please refer to FIG. 3E. FIG. 3E is a time sequence diagram of thesignals that the driving circuit 110 b transmits and receives inaccordance with some embodiments of the present disclosure. In oneembodiment, both the serial input data SDI and the monitoring Dmonduring the second period P2 have low voltage levels. Therefore, theoutput data SDO during the second period P2 has a low voltage level,which indicates that according to the cathode voltages monitored by thecomparators 111 of the driving circuits 110 a and 110 b the powervoltage VLED does not need to be stepped up.

In one embodiment, one or all of the monitoring data Dmon, the serialinput data SDI, and the output data SDO is digital data, which has ahigh logic level or a low logic level. In one embodiment, one or all ofthe monitoring data Dmon, the serial input data SDI, and the output dataSDO is analog data, which can have different voltage level, e.g., 0V,1V, 2V, 3V, and others alike.

Please refer to FIG. 1 and FIG. 4 . FIG. 4 is a circuit diagram of thedriving circuit 110 c in accordance with some embodiments of the presentdisclosure. The driving circuit 110 c includes the same components asthe driving circuit 110 b (i.e., the comparator 111, the serial inputinterface 112, the integrating unit 113, and the serial output interface114) and a feedback generator 115. Detailed description of the previousembodiments can be referred to. The feedback generator 115 is configuredto receive the output data SDO and generate the feedback control signalSFB to the power supply circuit 120. In some embodiments, the feedbackgenerator 115 is configured to extract the monitoring data DmonC in thesecond period P2, as shown in FIG. 3A, from the output data SDO. Themonitoring data DmonC reflect whether the cathode voltages of the LEDs140 coupled to the driving circuits 110 are lower than the thresholdvoltage. The feedback control signal SFB is generated to trigger thepower supply circuit to raise or maintain the power voltage VLED.

In the embodiment shown in FIG. 4 , the feedback controller 115 isincluded in the latest driving circuit 110 c, but the present disclosureis not limited thereto. In other embodiments, the functions of thefeedback controller 115 can be integrated into the power supply circuit120, and the output data SDO are directly transmitted to the powersupply circuit 120 from the driving circuit 110 c.

In some embodiments, the serial input data SDI and the output data SDOare transmitted among the driving circuits 110 a, 110 b, and 110 cthrough a serial transmission in a time-dividing manner. In other words,the serial input data SDI and the output data SDO can be transmittedthrough only one line, instead of two independent lines.

For most display devices on the market, the driver integrated circuits(IC) that control the currents passing through the light emitting diodes(LEDs) in the display device need a common bus system in order tocommunicate information about whether the driving voltage is largeenough to drive the LEDs. In this approach, extra pins are required forall driver ICs in order to communicate through a common bus system thatis different and independent from the driver ICs′ input/outputinterface, and thus the cost and complexity to manufacture the driverICs increase.

Thus, the power voltage VLED can be modulated according to the outputdata SDO. It is worth noted that the configuration between the drivingcircuit 110 c and the power supply circuit 120 does not intend to limitthe present disclosure. Person having ordinary skills in the art can usedifferent configuration between the driving circuit 110 c and the powersupply circuit 120 and still implement the disclosed driving circuits110 configured to modulate the power voltage VLED. In the embodimentwhere the output data SDO is digital data, the feedback generator 115can be further configured to transform the output data SDO into analogdata for the purpose of modulating the power voltage VLED.

Please refer to FIG. 5 . FIG. 5 is a circuit diagram of the drivingcircuit 110 c in accordance with some embodiments of the presentdisclosure. In one embodiment, the driving circuit 110 c does not havethe feedback generator 115 shown in FIG. 4 , and the output data SDO istransmitted to a microcontroller unit (MCU) 150. The microcontrollerunit 150 determines whether the power voltage VLED needs to be steppedup according to the output data SDO and then transmits a raise controlsignal RCON to the power supply circuit 120. The power supply circuit120 raises or maintains the power voltage VLED based on the raisecontrol signal RCON.

In conclusion, the driving circuits 110 in the various embodiments ofthe present disclosure can transmit the information regarding themonitored voltage of the corresponding LEDs 140 through the serial inputinterface 112 and the serial output interface 114. The serial inputinterface 112 and the serial output interface 114 and others alike arenormally included in most driving circuits, but in most cases theytransmit only the display data DD configured to control the current ofthe LEDs coupled to the driving circuits. On the contrary, in theembodiments of the present disclosure, the serial input interface 112and the serial output interface 114 are also configured to transmit theinformation regarding whether the power voltage VLED should be raised.

The present disclosure also provides a voltage modulation method. Pleaserefer to FIG. 6 . FIG. 6 is a flowchart of a voltage modulation method600 in accordance with some embodiments of the present disclosure. Thevoltage modulation method 600 includes steps S610, S620, S630, and S640.These steps can be performed through the configurations shown in theprevious embodiments of the present disclosure.

The step S610 is to determine whether a cathode voltage of a lightemitting diode is lower than a threshold value and generate a monitoringdata. For example, in the embodiment shown in FIG. 2 , the comparator111 determines whether the cathode voltage of the LED 140 bn is lowerthan the threshold value and generates the monitoring data Dmonaccordingly.

In one embodiment, the monitoring data has a first level in response tothe cathode voltage of the light emitting diode being lower than thethreshold value, and the monitoring data has a second level in responseto the cathode voltage of the light emitting diode being higher than thethreshold value. Detailed description of the previous embodiments can bereferred.

The step S620 is to receive a serial input data from a previous drivingcircuit. For example, in the embodiment shown in FIG. 2 , the serialinput interface 112 receives the serial input data SDI from the drivingcircuit 110 a and passes such data to the integrating unit 113.

The step S630 is to integrate the monitoring data and the serial inputdata to generate an output data. For example, in the embodiment shown inFIG. 2 , the integrating unit 113 integrates the monitoring data Dmonand the serial input data SDI and then generates the output data SDO.

In one embodiment, the output data has the first level in response tothe monitoring data having the first level or the serial input datahaving the first level, and the output data has the second level inresponse to the monitoring data having the second level and the serialinput data having the second level. Detailed description of the previousembodiments can be referred.

The step S640 is to transmit the output data to a following drivingcircuit or to feedback the output data to a power supply circuit inorder to modulate a power voltage VLED that the power circuit providesto the light emitting diode. For example, in the embodiment shown inFIG. 2 , the serial output interface 114 transmits the output data SDOto the driving circuit 110 c. In another example, as shown in FIG. 4 ,the feedback generator 115 feedbacks the output data SDO to the powersupply circuit 120. However, in the two examples, the goal is the same -to modulate the power voltage VLED that the power circuit 120 providesto the LEDs 140.

In one embodiment, the voltage modulation method 600 further includestransmitting the output data to a microcontroller unit configured todetermine whether the power voltage needs to be stepped up according tothe output data and to transmit a raise control signal to the powersupply circuit. For example, as in the embodiment shown in FIG. 5 , theoutput data SDO is transmitted to the microcontroller unit 150, and themicrocontroller unit 150 transmits the raise control signal RCON to thepower supply circuit 120. Detailed description of the previousembodiments can be referred.

In one embodiment, the voltage modulation method 600 further includesreceiving a display data from the previous driving circuit andtransmitting the display data to the following driving circuit. Thedisplay data is configured to control a current passing through thelight emitting diode in this embodiment. For example, as in theembodiments shown in FIG. 2 , FIG. 4 , and FIG. 5 , the serial inputinterface 112 receives the display data DD and transmits it to theserial output interface 114. Detailed description of the previousembodiments can be referred.

In one embodiment, integrating the monitoring data and the serial inputdata to generate the output data further includes bypassing a displaydata carried in the serial input data as the output data during a firstperiod and combining the monitoring data with the serial input data asthe output data during a second period. The first period and the secondperiod do not overlap. For example, as in the embodiments shown in FIG.2 and FIG. 3A, the integrating unit 113, during the first period P1,bypasses the display data DD carried in the serial input data SDI as theoutput data SDO and, during the second period P2, combines themonitoring data Dmon (which is the monitoring data DmonB during thesecond period P2) with the serial input data SDI(which is the monitoringdata DmonA during the second period P2) as the output data SDO (which isthe monitoring data DmonC during the second period P2).

In conclusion, through the voltage modulation method 600, informationabout voltage of the LEDs coupled to different driving circuits can becombined together and passed to a power supply circuit of a displaydevice so that the power supply circuit can modulate the driving voltageaccordingly.

Although the present invention has been described in considerable detailwith reference to certain embodiments thereof, other embodiments arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A driving circuit, configured to couple to alight emitting diode and a power supply circuit and modulate the powersupply circuit for providing power to the light emitting diode, thedriving circuit comprising: a comparator, configured to couple to thelight emitting diode and determine whether a cathode voltage of thelight emitting diode is lower than a threshold value and generate amonitoring data; a serial input interface, configured to receive aserial input data from a previous driving circuit; and an integratingunit, coupled to the comparator and the serial input interface andconfigured to integrate the monitoring data and the serial input data togenerate an output data, the output data being transmitted to afollowing driving circuit or feedbacked to the power supply circuit inorder to modulate a power voltage provided by the power circuit to thelight emitting diode.
 2. The driving circuit of claim 1, wherein: themonitoring data has a first level in response to the cathode voltage ofthe light emitting diode being lower than the threshold value; and themonitoring data has a second level in response to the cathode voltage ofthe light emitting diode being higher than the threshold value.
 3. Thedriving circuit of claim 2, wherein: the integrating unit generates theoutput data as the first level in response to the monitoring data havingthe first level or the serial input data having the first level; and theintegrating unit generates the output data as the second level inresponse to the monitoring data having the second level and the serialinput data having the second level.
 4. The driving circuit of claim 3,wherein the output data generated by the integrating unit with the firstlevel is configured to trigger the power supply circuit to raise thepower voltage.
 5. The driving circuit of claim 3, wherein the outputdata generated by the integrating unit with the second level isconfigured to trigger the power supply circuit to maintain the powervoltage.
 6. The driving circuit of claim 1, further comprising: afeedback output interface, configured to transmit the output data to thepower supply circuit.
 7. The driving circuit of claim 1, furthercomprising: a serial output interface, configured to transmit the outputdata to the following driving circuit.
 8. The driving circuit of claim7, further comprising: a microcontroller unit, coupled between theserial output interface and the power supply circuit and configured todetermine whether the power voltage needs to be stepped up according tothe output data and to transmit a raise control signal to the powersupply circuit.
 9. The driving circuit of claim 7, wherein the serialinput interface is configured to receive display data from the previousdriving circuit, the serial output interface is configured to transmitthe display data to the following driving circuit, and the display datais configured to control a current passing through the light emittingdiode.
 10. The driving circuit of claim 1, wherein the integrating unitintegrates the monitoring data and the serial input data in atime-dividing manner by: bypassing display data carried in the serialinput data as the output data during a first period; combining themonitoring data with the serial input data as the output data during asecond period; and the first period and the second period do notoverlap.
 11. The driving circuit of claim 10, wherein the drivingcircuit receives a control signal, the integrating unit operates in thesecond period in response to the control signal having a first level,and the integrating unit operates in the first period in response to thecontrol signal having a second level.
 12. A voltage modulation method ofa light emitting diode, comprising: determining whether a cathodevoltage of the light emitting diode is lower than a threshold value andgenerating a monitoring data; receiving a serial input data from aprevious driving circuit; integrating the monitoring data and the serialinput data to generate an output data; and transmitting the output datato a following driving circuit or feeding back the output data to apower supply circuit in order to modulate a power voltage that the powercircuit provides to the light emitting diode.
 13. The voltage modulationmethod of claim 12, wherein: the monitoring data has a first level inresponse to the cathode voltage of the light emitting diode being lowerthan the threshold value, and the monitoring data has a second level inresponse to the cathode voltage of the light emitting diode being higherthan the threshold value.
 14. The voltage modulation method of claim 13,wherein: the output data has the first level in response to themonitoring data having the first level or the serial input data havingthe first level; and the output data has the second level in response tothe monitoring data having the second level and the serial input datahaving the second level.
 15. The voltage modulation method of claim 12,further comprising: transmitting the output data to a microcontrollerunit configured to determine whether the power voltage needs to bestepped up according to the output data and to transmit a raise controlsignal to the power supply circuit.
 16. The voltage modulation method ofclaim 12, further comprising: receiving display data from the previousdriving circuit; and transmitting the display data to the followingdriving circuit; wherein the display data is configured to control acurrent passing through the light emitting diode.
 17. The voltagemodulation method of claim 12, wherein integrating the monitoring dataand the serial input data to generate the output data further includes:bypassing display data carried in the serial input data as the outputdata during a first period; and combining the monitoring data with theserial input data as the output data during a second period; wherein thefirst period and the second period do not overlap.
 18. The voltagemodulation method of claim 17, further comprising: receiving a controlsignal; operating in the second period in response to the control signalhaving a first level; and operating in the first period in response tothe control signal having a second level.